1. Field of the Invention
In general, the present invention relates to a device and method of recovering fluids from oil and gas wells. More particularly, the present invention increases the production rates in plunger lift wells by converting a single stage plunger lift system to a multiple stage plunger lift system with a new and improved plunger lift tool and method of using the same.
2. Description of the Prior Art
Typically, in plunger lift wells, a single plunger is used to move fluids such as oil and water from below the surface to the surface. Generally, the plunger travels from the lower end of the well to the surface under the propulsion of compressed gas that has been injected from the surface to the bottom of the well or has naturally developed in the well and then under the plunger. As the plunger rises, it lifts a column of fluid accumulated above the plunger to the surface where it is collected. After the fluid is discharged and the plunger has reached a designated height, the gas pressure is reduced and the plunger descends, under the influence of gravity, to the bottom of the well for another load of fluid. When the plunger hits the bottom or contacts fluid in the well, a mechanical valve is activated which then allows the gas pressure to build under the plunger, thus raising the plunger again and with it accumulated fluid.
It is contemplated to convert a single plunger system as described above to a dual stage system which incorporates the use of two plungers. A device referred to as a plunger lift tool, hereinafter referred to as “tool”, is incorporated for the conversion in the well and a second plunger added. Generally, the well is divided by the tool such that a plunger is located and operates below the tool and a second plunger is located and operates above the tool.
In operation, the first plunger is sent down the hole. Next, the tool is sent down the hole and selectively and removably positioned at a predetermined location above the first plunger. Finally, a second plunger is then sent down the hole. The positioned tool divides the well into two stages, a first stage for the first plunger to travel and a second stage for the added second plunger to travel. The first stage is defined by the distance of travel from the bottom of the well up to the location where the tool is positioned and the second stage is defined by the positioned tool to the top of the well.
In operation, the first plunger travels from the lower end of the well, through the first stage and pushes the accumulated oil through the tool into the second stage where the second plunger carries the oil to the surface. Although two stages are created with two different plungers in each stage, the basic operation is the same where the plungers rise under pressure and then fall back by gravity. When the first plunger hits the bottom of the well or contacts fluids, a mechanical valve is activated which then allows the gas pressure to build under the first plunger. Likewise, when the second plunger falls and hits the tool or contacts fluids, a mechanical valve is activated which then allows the gas pressure to build under the second plunger. Use of multiple plungers allows for a gas energy pocket under the tool to help lift the load of fluid on the second plunger on the next open cycle of the well.
Many problems are present in the prior art due to the fundamental functional requirements needed in operation of a multi-stage plunger lift system. In order to create the operational stages in the well, the tool must be able to make a seal with the tubing when set in position. Likewise, the seal has to be removably attached so that the tool can be retracted from the well for such things as replacing plungers in the bottom stage, under the tool. Currently, there are no known simple, functional, and cost effective methods in making a necessary seal and allow the tool to be extracted easily from the well.
Another potential limitation is due to the simple fact that different wells configurations cause different needs for creating seals for making separate zones. Some well tubing is connected with collars whereas others have joints. The prior art fails to provide a solution for creating such seals in multiple applications.
Still yet another example of a potential limitation is the difficulty of removing the tool from a well where fluid has accumulated above the tool. Due to the added weight of the standing fluid, the prior art methods associated with the industry do not easily allow removal of the necessary equipment with a slick line and is, thus, less functionally efficient.
Of note, in the current invention, a “plunger” is the device that would actually move up and down in the well whereas a “plunger lift tool” is a reference to the device that essentially is positioned in the well in a removably fixed position and does not travel up and down in the well to push fluids. In some of the prior art patents, such as U.S. Pat. No. 4,984,969 issued Jan. 15, 1991 to Fineberg, the term “plunger lift tool” as used is not to be confused with how the term is used in the current specification. It is believed that the aforementioned patent which is titled “Plunger Lift Tool” is actually what would be considered by the art to be simply a “plunger”. For clarity, the current invention uses the term “plunger” to mean the device that moves up and down in the well which is standard in the art. In the current invention, a “plunder lift tool” or “tool” refers to a device that is generally fixed in the well to create multiple zones or areas for multiple plungers to operate within and is a completely separate device from a plunger.
The above discussed limitations in the prior art is not exhaustive. The current invention provides an inexpensive, time saving, more reliable apparatus and method of using the same where the prior art fails.